1. Field of the Invention
The present invention is generally related to pressure infusion apparatus, and more particularly to disposable pressure cuffs having a flow-through pressure gauge.
2. Statement of the Prior Art
Liquids administered by intravenous injection, such as whole blood, plasma, saline and dextrose solutions, are typically supplied in disposable infusion bags which are most often made of a flexible, transparent plastic having an outlet port or delivery tube which is adapted to be punctured by a coupler of a recipient set. In use, the infusion bag is suspended above the patient and the liquid contained therein is permitted to flow by gravity into the patient's vein. There are many situations, particularly when the infusion bag is nearly empty or in cases of severe hemorrhage and shock, where the administration of fluid by gravity flow with conventionally employed infusion bags is unacceptably slow.
Various pressure infusion apparatus have been used in the past to overcome such problems of slow delivery. See, for example, U.S. Pat. No. 2,766,907, issued Oct. 16, 1956 to Wallace, Jr.; U.S. Pat. No. 3,153,414, issued Oct. 20, 1964 to Beall et al.; U.S. Pat. No. 4,090,514, issued May 23, 1978 to Hinck et al.; U.S. Pat. No. 4,507,116, issued Mar. 26, 1985 to Leibinsohn; and U.S. Pat. No. 4,735,613, issued Apr. 5, 1988 to Bellin et al. Such known pressure infusion apparatus characteristically comprises bladder means for maintaining a fluid under pressure, means forming a pocket with the bladder means for holding an infusion bag against the bladder means for pressurizing the infusion bag by transmission of pressure from the pressurized bladder means to the infusion bag, and pressurization means which is coupled to the bladder means for introducing a flow of the fluid into the bladder means and thereby pressurizing same.
With most pressure infusion apparatus, the bladder means is formed of an elastomeric material that is contained in an outer shell. For example, in U.S. Pat. No. 4,735,613 referenced above, Bellin et al. disclose a pressure bag that is formed of two sheets of plastic material fastened together along their edges. A fabric mesh is secured at its opposite sides to a fabric sheet and, thus, forms a pocket for holding an infusion bag and the pressure bag in engagement with each other. One problem that is presented by such conventionally-formed pressure infusion apparatus is the amount of visibility provided by the fabric mesh, for observing the infusion bag during administration of the fluid contained therein. Persons who would use such pressure infusion apparatus according to Bellin et al. would experience some difficulty in monitoring the progress of the administered fluid.
Other known pressure infusion apparatus, including those described in the patents noted above, provide better opportunities for observing the infusion bags during administration of the fluid contained therein by using a flexible, transparent sheet, which is attached to the bladder means for holding the infusion bag against the bladder means. However, various complicated means for joining such transparent sheets to the bladder means (e.g., sewn stitching or hook-and-pile means) in these known pressure infusion apparatus greatly increases their fabrication costs.
A suitable disposable pressure cuff is disclosed in the above-referenced copending application Ser. No. 415,097, filed Sept. 29, 1989. Various means for pressurizing such pressure cuffs are known in the prior art, but an inflation, or "squeeze" bulb is typically used as the pressurization means to minimize manufacturing costs. Providing a single-ended inflation bulb with check valves according to the above-referenced copending application Ser. No. 415,209, filed Sept. 29, 1989, further avoids problems of leakage which have been experienced by double-ended inflation bulbs of the prior art.
In order to provide fully-disposable pressure infusion systems, however, it is necessary to include adequate means for monitoring pressures within the bladder means. A simple tubular pressure gauge is shown and claimed in U.S. Pat. No. 4,735,613, referenced above. Nevertheless, the pressure gauge disclosed in U.S. Pat. No. 4,735,613 suffers from disadvantage of having to be installed within the bladder means. A more versatile pressure gauge, which has the capability of selective placement within the pressure infusion system by the user, would be desirable.